Nanocarbon such as carbon nanofiber, carbon nanotube or onion-like carbon has functions such as a high conductive property and an excellent electromagnetic wave absorption property, and is expected to be applied in various fields.
As the methods for producing nanocarbon using a low hydrocarbon as a raw material, for example, production methods by arc discharge method, by CVD (Chemical Vapor Deposition) method, by a method using a fluidized bed reactor and the like have been known. The production method by arc discharge method is disclosed in PTL 1, for example. The production method by CVD method is disclosed in PTLs 2 and 3, for example. The production method using a fluidized bed reactor is disclosed in PTL 4, for example.
FIG. 7 is a schematic drawing showing the device for producing carbon nanotube by arc discharge method disclosed in PTL 1. As shown in the drawing, an upper flange 101, a lower flange 102, a front flange 103 and a back flange 104 are attached to a reaction vessel (a vacuum chamber) 100. In the reaction vessel 100, a bar negative electrode 105 as a carbon electrode and a bar electrode for producing carbon nanotube (positive electrode) 106, which contains carbon and a non-magnetic transition metal, are placed facing each other. The positive electrode 106 is placed with a constant distance from the negative electrode 105 by an advancing and retreating structure 107. The negative electrode 105 is connected to a cathode terminal 108, and the positive electrode 106 is connected to an anode terminal 109. These cathode terminal 108 and anode terminal 109 are connected to a direct-current power supply (not described in the drawing).
In the production device by arc discharge method shown in FIG. 7, arc discharge is caused between the positive electrode 106 and the negative electrode 105 in the reaction vessel 100 replaced with helium gas. From this, the tip of the positive electrode 106 evaporates, and spray-like fine particles of carbon steam and the non-magnetic transition metal generate. Thus generated spray-like fine particles cohere and precipitate/accumulate, and thus a single layer carbon nanotube accumulates, for example on the outer surface around the root of the negative electrode 105.
Further, FIG. 8 is a schematic drawing showing a device for synthesizing carbon nanotube by CVD method (a horizontal electric furnace) disclosed in PTL 2. As shown in the drawing, around a reaction tube 200, an electric heater 201 for heating the reaction tube 200 is placed. In the reaction tube 200, a base plate containing an iron salt 202 is placed as the main catalyst, and a base plate containing a molybdate 203 is placed as the co-catalyst.
In the production device by CVD method shown in FIG. 8, the inside of the reaction tube 200 is heated to a certain temperature. Then, a carbon source such as methane gas is fed in the reaction tube 200 with an inert gas such as argon gas and is reacted at a certain temperature, and thus carbon nanotube is vapor-deposited.
Furthermore, FIG. 9 is a schematic drawing showing the device for producing fiber nanocarbon using a fluidized bed reactor disclosed in PTL 4. As shown in the drawing, the device for producing fiber nanocarbon has: a fluidized bed reactor 301 having a heating unit 300 for heating the inside; a first gas supplying unit 303 for supplying a reductive gas 302 to the fluidized bed reactor 301; a carbon material supplying unit 305 for supplying a carbon material 304 in the fluidized bed reactor 301 in a gas state; a second gas supplying unit 307 for supplying an inert gas including no carbon 306 to the fluidized bed reactor 301; and an exhaust line 309 for exhausting from the fluidized bed reactor 301 a scattering particle 308 including gas G and the fiber nanocarbon obtained. The fluidized bed reactor 301 is composed of a fluidized bed part 301A for forming the fluidized bed, and a free board part 301B on the fluidized bed part 301A in a state that it is connected to the fluidized bed part 301A. Furthermore, the fluidized bed reactor 301 is filled with a catalyst fluid material 310, to which a carrier supporting a catalyst is bound through a binder. In addition, a particle collecting unit 311 for collecting the particles is connected to the exhaust line 309.
In the production device shown in FIG. 9, the reductive gas 302 is supplied to the fluidized bed reactor 301 by the first gas supplying unit 303 and the form of the catalyst is made into metal. Next, the carbon material 304 is supplied to the fluidized bed reactor 301 in a gas state by the carbon material supplying unit 305, and fiber nanocarbon is deposited on the catalyst at a certain reaction temperature. Then, by raising the temperature inside the fluidized bed reactor 301 higher than the reaction temperature by the heating unit 300, the binder forming the catalyst fluid material 310 is pulverized by thermal decomposition or the like, and the function as a fluid material is lost. The material, which has lost the fluidity function, becomes an aggregate of carriers or a bound body thereof, and is pulverized. Then, it is exhausted with the gas G outside from the free board part 301B of the fluidized bed reactor 301 through the exhaust line 309 as the scattering particle 308. The scattering particle 308 exhausted is collected by the particle collecting unit 311. Fiber nanocarbon is separated from the thus collected scattering particle 308.